Projector devices are required to illuminate images evenly with sufficient color rendering against a rectangular screen, and therefore, as a light source, metal halide lamps that enclose mercury and metal halogen compounds have been used. In addition, recently, further size reductions and the employment of a point light source have advanced and those with an extremely short distance between the electrodes have been put to practical use. Given the background, recently, in place of metal halide lamps, high-pressure discharge lamps having an extremely high mercury vapor pressure, such as 20 MPa (approximately 197 atmospheres) or greater have been used. These lamps have a limited arc spread and a further increase in light output do to their high mercury vapor pressure.
As an above-mentioned lamp, for example, an ultra high-pressure discharge lamp having a quartz glass arc tube with a pair of electrodes that face each other at a 2 mm or less interval that encloses mercury at 0.15 mg/mm3 or greater, a noble gas, and a halogen in the range of 10−6 μmol/mm3 to 10−2 μmol/mm3 can be used. This type of discharge lamp and its lighting device are, for example disclosed in Japanese Unexamined Application Publication No. H02-148561. The high-pressure discharge lamp disclosed in Japanese Unexamined Application Publication H02-148561 is one in which the inner mercury vapor pressure at a normal power lighting is 15 MPa to 35 MPa, and a halide is enclosed in the arc tube in the range from 10−6 μmol/mm3 to 10−2 μmol/mm3. It has a pair of electrodes in the arc tube and by having a protruding part around the center of the electrode tip, it limits the generation of the so-called arc jump phenomenon in which the location of the discharge arc is not stable at the center or periphery of the electrode tips and moves around. In addition, a lighting device, which is comprised of a DC/DC converter, a DC/AC converter, and a high-pressure generation device, applies an alternating current between the above-mentioned pair of electrodes. Thus, lighting is carried out.
Recently, projectors are provided not only for presentations but also for movie viewing as well. However, it has been known from the past that single-panel projectors that combine a light bulb and color wheel have poor color reproducibility of the projected images. To resolve the problem, for example, Japanese Unexamined Application Publication H08-505031 exists. This literature lists a method in which a lamp is lit by modulating the light intensity for each segment that is separated by the color wheel.